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Title: SU-F-T-135: A Retrospective Analysis of the Impact of Range Uncertainty in Brain Patients

Abstract

Purpose: We retrospectively evaluate the dosimetric impact of a 3.5% range uncertainty on CTV coverage and normal organ toxicity for a cohort of brain patients. Methods: Twenty treatment plans involving 20 brain cancer patients treated with Mevions S250 were reviewed. Forty uncertain plans were made by changing the ranges in original plans by ±3.5% while keeping all devices unchanged. Fidelity to the original plans was evaluated with gamma index. Changes in generalized equivalent uniform dose (gEUD) were reported for the following structures: CTV coverage, brainstem, optic chiasm, and optic nerves. Comparisons were made by plotting the relevant endpoints from the uncertain plans as a function of the same endpoints from the original clinical plan. Results: Gamma-index analysis resulted in a 50% pass rate of the uncertain plans using a 90% passing rate and 3%/3mm criterion. A 9.5% decrease in the slope of gEUD plot for the CTV was observed for the 3.5% downward range shift. However, the change in slope did not result in a gEUD change greater than 1.1% for the CTV. The slopes of the gEUD plots for normal structures increased by 3.1% 3.9% 2.4% and 0.2% for the chiasm, brainstem, left optic nerve and right optic nervemore » respectively. The maximum deviation from the gEUD of the clinical plan for normal structures was: 64% in the chiasm, 31% for the brainstem, and 19% for both optic nerves. Conclusion: A retrospective review shows moderate radiobiological impact of range uncertainty in passively scattered proton therapy with sporadic catastrophe. The linear regression analysis on the statistical data indicates a systematic deviation of gEUD from treatment planning in the light of range uncertainty.« less

Authors:
; ; ; ; ; ; ; ; ; ; ;  [1]
  1. Washington University School of Medicine, Saint Louis, MO (United States)
Publication Date:
OSTI Identifier:
22642376
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; BRAIN; NERVES; OPTICS; PATIENTS; PLANNING; PROTON BEAMS; REGRESSION ANALYSIS; STATISTICAL DATA; VISIBLE RADIATION

Citation Formats

Grantham, K, Santanam, L, Goddu, S, Sun, B, Zhang, T, Mutic, S, Robinson, C, Huang, J, Perkins, S, Tsien, C, Bradley, J, and Zhao, T. SU-F-T-135: A Retrospective Analysis of the Impact of Range Uncertainty in Brain Patients. United States: N. p., 2016. Web. doi:10.1118/1.4956271.
Grantham, K, Santanam, L, Goddu, S, Sun, B, Zhang, T, Mutic, S, Robinson, C, Huang, J, Perkins, S, Tsien, C, Bradley, J, & Zhao, T. SU-F-T-135: A Retrospective Analysis of the Impact of Range Uncertainty in Brain Patients. United States. doi:10.1118/1.4956271.
Grantham, K, Santanam, L, Goddu, S, Sun, B, Zhang, T, Mutic, S, Robinson, C, Huang, J, Perkins, S, Tsien, C, Bradley, J, and Zhao, T. Wed . "SU-F-T-135: A Retrospective Analysis of the Impact of Range Uncertainty in Brain Patients". United States. doi:10.1118/1.4956271.
@article{osti_22642376,
title = {SU-F-T-135: A Retrospective Analysis of the Impact of Range Uncertainty in Brain Patients},
author = {Grantham, K and Santanam, L and Goddu, S and Sun, B and Zhang, T and Mutic, S and Robinson, C and Huang, J and Perkins, S and Tsien, C and Bradley, J and Zhao, T},
abstractNote = {Purpose: We retrospectively evaluate the dosimetric impact of a 3.5% range uncertainty on CTV coverage and normal organ toxicity for a cohort of brain patients. Methods: Twenty treatment plans involving 20 brain cancer patients treated with Mevions S250 were reviewed. Forty uncertain plans were made by changing the ranges in original plans by ±3.5% while keeping all devices unchanged. Fidelity to the original plans was evaluated with gamma index. Changes in generalized equivalent uniform dose (gEUD) were reported for the following structures: CTV coverage, brainstem, optic chiasm, and optic nerves. Comparisons were made by plotting the relevant endpoints from the uncertain plans as a function of the same endpoints from the original clinical plan. Results: Gamma-index analysis resulted in a 50% pass rate of the uncertain plans using a 90% passing rate and 3%/3mm criterion. A 9.5% decrease in the slope of gEUD plot for the CTV was observed for the 3.5% downward range shift. However, the change in slope did not result in a gEUD change greater than 1.1% for the CTV. The slopes of the gEUD plots for normal structures increased by 3.1% 3.9% 2.4% and 0.2% for the chiasm, brainstem, left optic nerve and right optic nerve respectively. The maximum deviation from the gEUD of the clinical plan for normal structures was: 64% in the chiasm, 31% for the brainstem, and 19% for both optic nerves. Conclusion: A retrospective review shows moderate radiobiological impact of range uncertainty in passively scattered proton therapy with sporadic catastrophe. The linear regression analysis on the statistical data indicates a systematic deviation of gEUD from treatment planning in the light of range uncertainty.},
doi = {10.1118/1.4956271},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}